[show abstract][hide abstract] ABSTRACT: Alternative and ecological strategies are necessary and demanded for disease management in order to reduce the use of pesticides in agriculture. Thus, the use of biological control agents such as plant growth-promoting rhizobacteria (PGPR) or several strains of the beneficial fungus Trichoderma spp. to combat plant diseases is the basis of biocontrol of plant pathogens and is a good approach to reach this healthy and environmentally adequate objective.
[show abstract][hide abstract] ABSTRACT: Using the TrichoEST database, generated in a previous functional genomics project from the beneficial filamentous fungus Trichoderma harzianum, a gene named Thkel1, which codes for a putative kelch-repeat protein, was isolated and characterized. Silencing of this gene in T. harzianum leads to a reduction of glucosidase activity and mycelial growth under abiotic stress conditions. Expression of this gene in Arabidopsis enhances plant tolerance to salt and osmotic stresses, accompanied by an increase in glucosidase activity and a reduction of abscisic acid levels compared to those observed in wild-type plants. Data presented throughout this article suggest the high value of T. harzianum as a source of genes able to facilitate the achievement of producing plants resistant to abiotic stresses without alteration of their phenotype.
Journal of plant physiology 04/2011; 168(11):1295-302. · 2.50 Impact Factor
[show abstract][hide abstract] ABSTRACT: The synthesis of reactive oxygen species (ROS) is one of the first events following pathogenic interactions in eukaryotic cells, and NADPH oxidases are involved in the formation of such ROS. The nox1 gene of Trichoderma harzianum was cloned, and its role in antagonism against phytopathogens was analyzed in nox1-overexpressed transformants. The increased levels of nox1 expression in these transformants were accompanied by an increase in ROS production during their direct confrontation with Pythium ultimum. The transformants displayed an increased hydrolytic pattern, as determined by comparing protease, cellulase, and chitinase activities with those for the wild type. In confrontation assays against P. ultimum the nox1-overexpressed transformants were more effective than the wild type, but not in assays against Botrytis cinerea or Rhizoctonia solani. A transcriptomic analysis using a Trichoderma high-density oligonucleotide (HDO) microarray also showed that, compared to gene expression for the interaction of wild-type T. harzianum and P. ultimum, genes related to protease, cellulase, and chitinase activities were differentially upregulated in the interaction of a nox1-overexpressed transformant with this pathogen. Our results show that nox1 is involved in T. harzianum ROS production and antagonism against P. ultimum.
Applied and environmental microbiology 03/2011; 77(9):3009-16. · 3.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: The ability of some Trichoderma strains, a biological control agent, to overcome extreme environmental conditions has previously been reported and related to heat-shock proteins (HSPs). These proteins are induced environmentally and are involved in important processes, acting as molecular chaperones in all organisms. In a previous study, we demonstrated, by overexpression, that the Trichoderma harzianum hsp70 gene conferred tolerance to heat and other abiotic stresses to this fungus. In this work, we investigate the function of the T. harzianum T34 hsp70 gene in Arabidopsis thaliana. We analyze transgenic plant responses under adverse environmental conditions and the expression levels of a set of seven stress genes, using quantitative RT-PCR. As expected, transgenic plants expressing the T. harzianum hsp70 gene exhibited enhanced tolerance to heat stress. In addition, they did not show growth inhibition and, after heat pre-treatment, transgenic seedlings were more tolerant to osmotic, salt and oxidative stresses with respect to the wild-type behavior. Transgenic lines also had increased transcript levels of the Na(+)/H(+) exchanger 1 (SOS1) and ascorbate peroxidase 1 (APX1) genes, involved in salt and oxidative stress responses, respectively. However, the heat-shock factor (HSF) and four HSP genes tested were down-regulated in 35S:hsp70 plants. Overall, our results indicate that hsp70 confers tolerance to heat and other abiotic stresses and that the fungal HSP70 protein acts as a negative regulator of the HSF transcriptional activity in Arabidopsis.
Journal of plant physiology 05/2010; 167(8):659-65. · 2.50 Impact Factor
[show abstract][hide abstract] ABSTRACT: All organisms share similar mechanisms in the heat shock response, such as synthesis of conserved heat shock proteins. Here, we report on the cloning, characterization and functional analysis of a Trichoderma harzianum T34 hsp70 gene. The expression of this gene was evaluated in cultures grown in abiotic stress conditions. An increased level of expression was detected when the fungus was grown at 37 or 41 degrees C, as well as in the presence of oxidative or osmotic agents. The overexpression of hsp70 in T. harzianum T34 gave rise to transformants with higher quantities of biomass obtained after heat shock treatment. In addition, these transformants showed an enhanced tolerance to oxidative, osmotic and salt stresses when conidia were previously treated at 45 degrees C for 2h.
Fungal Genetics and Biology 10/2008; 45(11):1506-13. · 3.26 Impact Factor
[show abstract][hide abstract] ABSTRACT: An EST showing high values of identity with genes coding for small heat shock proteins (sHSPs) was selected from an EST library collection of Trichoderma virens T59. The cDNA gene (hsp23) with a sequence size of 645 bp long was amplified by PCR. The expression of this gene was evaluated in cultures grown at temperatures ranging from 4 to 41 degrees C. An increased level of expression was detected when the fungus was grown at extreme temperatures (4, 10 or 41 degrees C). A high-expression level was also observed when the fungus was grown in 10% ethanol for 4 h. The hsp23 gene was present as a unique copy in the T. virens genome, and a homologous gene was also present in other five investigated Trichoderma species. Strain T. harzianum T34 was transformed with the hsp23 gene from T. virens T59 under the control of the pki (pyruvate kinase) promoter from T. reesei and the ble (phleomycin resistance) gene as selection marker. Statistically significant differences were detected between the strains T34 and two selected transformants in the biomass quantities obtained after heat shock treatment and in the colony diameters after incubation at 4 degrees C for 2 months.
Current Genetics 08/2007; 52(1):45-53. · 2.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: A Gram-positive, aerobic, long-rod-shaped, non-spore-forming bacterium (strain PPLB(T)) was isolated from soil mixed with Iberian pig hair. This actinomycete showed keratinase activity in vitro when chicken feathers were added to the culture medium. Strain PPLB(T) was oxidase-negative and catalase-positive and produced lipase and esterase lipase. This actinomycete grew at 40 degrees C on nutrient agar and in the same medium containing 5 % (w/v) NaCl. Growth was observed with many different carbohydrates as the sole carbon source. On the basis of 16S rRNA gene sequence similarity, strain PPLB(T) was shown to belong to the genus Terrabacter of the family Intrasporangiaceae. Strain PPLB(T) showed 98.8 % 16S rRNA gene sequence similarity to Terrabacter tumescens. Chemotaxonomic data, such as the main ubiquinone (MK-8), the main polar lipids (phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylinositol) and the main fatty acids (i-C(15 : 0), ai-C(15 : 0), i-C(16 : 0) and ai-C(17 : 0)) supported the affiliation of strain PPLB(T) to the genus Terrabacter. The G+C content of the DNA was 71 mol%. The results of DNA-DNA hybridization (36.6 % relatedness between Terrabacter tumescens and strain PPLB(T)) and physiological and biochemical tests suggested that strain PPLB(T) belongs to a novel species of the genus Terrabacter, for which the name Terrabacter terrae sp. nov. is proposed. The type strain is PPLB(T) (=CECT 3379T=LMG 22921T).
International journal of systematic and evolutionary microbiology 12/2005; 55(Pt 6):2491-5. · 2.11 Impact Factor